ClearCase / Support for checking out from a tag and auto-creation of config specs

A major limitation of the ClearCase plugin so far has been the missing support for checking out from a tag. As a consequence, the Maven release plugin could not be used. I implemented checking out from a tag, by supporting the automatic creation of config specs.

The ClearCase SCM provider so far forced the user to create a config spec file at an external location and provide a link to it within the SCM url, e.g.:

scm:clearcase:my_module_view:\\myserver\clearcase\configspecs\my_module.txt

This URL format is still supported as it gives the user a maximum flexibility regarding config specs. However, it is quite unconvenient for users to provide config spec files in an external location. And for checking out from a tag, the config spec needs to be rewritten anyway. So, as an alternative, the user now can provide a SCM url like the following:

scm:clearcase:my_module_view:load /MY_VOB/my/project/directory

Such an url contains one load rule instead of a config spec file location. It is used by the ClearCase plugin to generate the following config spec in case no version tag has been specified:

element * CHECKEDOUT
element * /main/LATEST
load <load_directory>

In case a tag has been specified, the following config spec is created:

element * CHECKEDOUT
element * <tag>
element -directory * /main/LATEST
load <load_directory>

I expect these auto-generated config specs to be sufficient and appropriate in at least 80% of the cases. The new functionality improves the ClearCase SCM integration significantly in these cases (much easier to use and more powerful). So, please apply the attached patch for maven-scm-provider-clearcase, including a patch for the documentation site. As the current URL format is still fully supported, this patch should not affect existing builds.

(Afterwards, the maven-release-manager used by the Release plugin, can easily be completed by a ClearCase-specific ScmTranslator implementation to make the Release plugin fully usable with ClearCase.)